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Revision 1.55 by root, Sun Oct 22 00:49:29 2006 UTC vs.
Revision 1.111 by root, Mon Aug 13 12:08:13 2007 UTC

5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use IO::AIO; 7 use IO::AIO;
8 8
9 aio_open "/etc/passwd", O_RDONLY, 0, sub { 9 aio_open "/etc/passwd", O_RDONLY, 0, sub {
10 my ($fh) = @_; 10 my $fh = shift
11 or die "/etc/passwd: $!";
11 ... 12 ...
12 }; 13 };
13 14
14 aio_unlink "/tmp/file", sub { }; 15 aio_unlink "/tmp/file", sub { };
15 16
16 aio_read $fh, 30000, 1024, $buffer, 0, sub { 17 aio_read $fh, 30000, 1024, $buffer, 0, sub {
17 $_[0] > 0 or die "read error: $!"; 18 $_[0] > 0 or die "read error: $!";
18 }; 19 };
19 20
20 use IO::AIO 2; # version has aio objects 21 # version 2+ has request and group objects
22 use IO::AIO 2;
21 23
24 aioreq_pri 4; # give next request a very high priority
22 my $req = aio_unlink "/tmp/file", sub { }; 25 my $req = aio_unlink "/tmp/file", sub { };
23 $req->cancel; # cancel request if still in queue 26 $req->cancel; # cancel request if still in queue
24 27
25 # AnyEvent 28 my $grp = aio_group sub { print "all stats done\n" };
29 add $grp aio_stat "..." for ...;
30
31 # AnyEvent integration
26 open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!"; 32 open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
27 my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb }); 33 my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
28 34
29 # Event 35 # Event integration
30 Event->io (fd => IO::AIO::poll_fileno, 36 Event->io (fd => IO::AIO::poll_fileno,
31 poll => 'r', 37 poll => 'r',
32 cb => \&IO::AIO::poll_cb); 38 cb => \&IO::AIO::poll_cb);
33 39
34 # Glib/Gtk2 40 # Glib/Gtk2 integration
35 add_watch Glib::IO IO::AIO::poll_fileno, 41 add_watch Glib::IO IO::AIO::poll_fileno,
36 in => sub { IO::AIO::poll_cb; 1 }; 42 in => sub { IO::AIO::poll_cb; 1 };
37 43
38 # Tk 44 # Tk integration
39 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "", 45 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
40 readable => \&IO::AIO::poll_cb); 46 readable => \&IO::AIO::poll_cb);
41 47
42 # Danga::Socket 48 # Danga::Socket integration
43 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => 49 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
44 \&IO::AIO::poll_cb); 50 \&IO::AIO::poll_cb);
45 51
46
47=head1 DESCRIPTION 52=head1 DESCRIPTION
48 53
49This module implements asynchronous I/O using whatever means your 54This module implements asynchronous I/O using whatever means your
50operating system supports. 55operating system supports.
51 56
57Asynchronous means that operations that can normally block your program
58(e.g. reading from disk) will be done asynchronously: the operation
59will still block, but you can do something else in the meantime. This
60is extremely useful for programs that need to stay interactive even
61when doing heavy I/O (GUI programs, high performance network servers
62etc.), but can also be used to easily do operations in parallel that are
63normally done sequentially, e.g. stat'ing many files, which is much faster
64on a RAID volume or over NFS when you do a number of stat operations
65concurrently.
66
67While most of this works on all types of file descriptors (for
68example sockets), using these functions on file descriptors that
69support nonblocking operation (again, sockets, pipes etc.) is very
70inefficient. Use an event loop for that (such as the L<Event|Event>
71module): IO::AIO will naturally fit into such an event loop itself.
72
52Currently, a number of threads are started that execute your read/writes 73In this version, a number of threads are started that execute your
53and signal their completion. You don't need thread support in your libc or 74requests and signal their completion. You don't need thread support
54perl, and the threads created by this module will not be visible to the 75in perl, and the threads created by this module will not be visible
55pthreads library. In the future, this module might make use of the native 76to perl. In the future, this module might make use of the native aio
56aio functions available on many operating systems. However, they are often 77functions available on many operating systems. However, they are often
57not well-supported (Linux doesn't allow them on normal files currently, 78not well-supported or restricted (GNU/Linux doesn't allow them on normal
58for example), and they would only support aio_read and aio_write, so the 79files currently, for example), and they would only support aio_read and
59remaining functionality would have to be implemented using threads anyway. 80aio_write, so the remaining functionality would have to be implemented
81using threads anyway.
60 82
61Although the module will work with in the presence of other threads, it is 83Although the module will work in the presence of other (Perl-) threads,
62currently not reentrant, so use appropriate locking yourself, always call 84it is currently not reentrant in any way, so use appropriate locking
63C<poll_cb> from within the same thread, or never call C<poll_cb> (or other 85yourself, always call C<poll_cb> from within the same thread, or never
64C<aio_> functions) recursively. 86call C<poll_cb> (or other C<aio_> functions) recursively.
87
88=head2 EXAMPLE
89
90This is a simple example that uses the Event module and loads
91F</etc/passwd> asynchronously:
92
93 use Fcntl;
94 use Event;
95 use IO::AIO;
96
97 # register the IO::AIO callback with Event
98 Event->io (fd => IO::AIO::poll_fileno,
99 poll => 'r',
100 cb => \&IO::AIO::poll_cb);
101
102 # queue the request to open /etc/passwd
103 aio_open "/etc/passwd", O_RDONLY, 0, sub {
104 my $fh = shift
105 or die "error while opening: $!";
106
107 # stat'ing filehandles is generally non-blocking
108 my $size = -s $fh;
109
110 # queue a request to read the file
111 my $contents;
112 aio_read $fh, 0, $size, $contents, 0, sub {
113 $_[0] == $size
114 or die "short read: $!";
115
116 close $fh;
117
118 # file contents now in $contents
119 print $contents;
120
121 # exit event loop and program
122 Event::unloop;
123 };
124 };
125
126 # possibly queue up other requests, or open GUI windows,
127 # check for sockets etc. etc.
128
129 # process events as long as there are some:
130 Event::loop;
131
132=head1 REQUEST ANATOMY AND LIFETIME
133
134Every C<aio_*> function creates a request. which is a C data structure not
135directly visible to Perl.
136
137If called in non-void context, every request function returns a Perl
138object representing the request. In void context, nothing is returned,
139which saves a bit of memory.
140
141The perl object is a fairly standard ref-to-hash object. The hash contents
142are not used by IO::AIO so you are free to store anything you like in it.
143
144During their existance, aio requests travel through the following states,
145in order:
146
147=over 4
148
149=item ready
150
151Immediately after a request is created it is put into the ready state,
152waiting for a thread to execute it.
153
154=item execute
155
156A thread has accepted the request for processing and is currently
157executing it (e.g. blocking in read).
158
159=item pending
160
161The request has been executed and is waiting for result processing.
162
163While request submission and execution is fully asynchronous, result
164processing is not and relies on the perl interpreter calling C<poll_cb>
165(or another function with the same effect).
166
167=item result
168
169The request results are processed synchronously by C<poll_cb>.
170
171The C<poll_cb> function will process all outstanding aio requests by
172calling their callbacks, freeing memory associated with them and managing
173any groups they are contained in.
174
175=item done
176
177Request has reached the end of its lifetime and holds no resources anymore
178(except possibly for the Perl object, but its connection to the actual
179aio request is severed and calling its methods will either do nothing or
180result in a runtime error).
181
182=back
65 183
66=cut 184=cut
67 185
68package IO::AIO; 186package IO::AIO;
69 187
71use strict 'vars'; 189use strict 'vars';
72 190
73use base 'Exporter'; 191use base 'Exporter';
74 192
75BEGIN { 193BEGIN {
76 our $VERSION = '2.0'; 194 our $VERSION = '2.4';
77 195
78 our @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat 196 our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
79 aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink 197 aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
80 aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move 198 aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link
81 aio_group); 199 aio_move aio_copy aio_group aio_nop aio_mknod aio_load aio_rmtree aio_mkdir
82 our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs); 200 aio_chown aio_chmod aio_utime aio_truncate);
201 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));
202 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
203 min_parallel max_parallel max_idle
204 nreqs nready npending nthreads
205 max_poll_time max_poll_reqs);
83 206
84 @IO::AIO::GRP::ISA = 'IO::AIO::REQ'; 207 @IO::AIO::GRP::ISA = 'IO::AIO::REQ';
85 208
86 require XSLoader; 209 require XSLoader;
87 XSLoader::load ("IO::AIO", $VERSION); 210 XSLoader::load ("IO::AIO", $VERSION);
88} 211}
89 212
90=head1 FUNCTIONS 213=head1 FUNCTIONS
91 214
92=head2 AIO FUNCTIONS 215=head2 AIO REQUEST FUNCTIONS
93 216
94All the C<aio_*> calls are more or less thin wrappers around the syscall 217All the C<aio_*> calls are more or less thin wrappers around the syscall
95with the same name (sans C<aio_>). The arguments are similar or identical, 218with the same name (sans C<aio_>). The arguments are similar or identical,
96and they all accept an additional (and optional) C<$callback> argument 219and they all accept an additional (and optional) C<$callback> argument
97which must be a code reference. This code reference will get called with 220which must be a code reference. This code reference will get called with
100syscall has been executed asynchronously. 223syscall has been executed asynchronously.
101 224
102All functions expecting a filehandle keep a copy of the filehandle 225All functions expecting a filehandle keep a copy of the filehandle
103internally until the request has finished. 226internally until the request has finished.
104 227
105All requests return objects of type L<IO::AIO::REQ> that allow further 228All functions return request objects of type L<IO::AIO::REQ> that allow
106manipulation of those requests while they are in-flight. 229further manipulation of those requests while they are in-flight.
107 230
108The pathnames you pass to these routines I<must> be absolute and 231The pathnames you pass to these routines I<must> be absolute and
109encoded in byte form. The reason for the former is that at the time the 232encoded as octets. The reason for the former is that at the time the
110request is being executed, the current working directory could have 233request is being executed, the current working directory could have
111changed. Alternatively, you can make sure that you never change the 234changed. Alternatively, you can make sure that you never change the
112current working directory. 235current working directory anywhere in the program and then use relative
236paths.
113 237
114To encode pathnames to byte form, either make sure you either: a) 238To encode pathnames as octets, either make sure you either: a) always pass
115always pass in filenames you got from outside (command line, readdir 239in filenames you got from outside (command line, readdir etc.) without
116etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode 240tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
117your pathnames to the locale (or other) encoding in effect in the user 241your pathnames to the locale (or other) encoding in effect in the user
118environment, d) use Glib::filename_from_unicode on unicode filenames or e) 242environment, d) use Glib::filename_from_unicode on unicode filenames or e)
119use something else. 243use something else to ensure your scalar has the correct contents.
244
245This works, btw. independent of the internal UTF-8 bit, which IO::AIO
246handles correctly wether it is set or not.
120 247
121=over 4 248=over 4
249
250=item $prev_pri = aioreq_pri [$pri]
251
252Returns the priority value that would be used for the next request and, if
253C<$pri> is given, sets the priority for the next aio request.
254
255The default priority is C<0>, the minimum and maximum priorities are C<-4>
256and C<4>, respectively. Requests with higher priority will be serviced
257first.
258
259The priority will be reset to C<0> after each call to one of the C<aio_*>
260functions.
261
262Example: open a file with low priority, then read something from it with
263higher priority so the read request is serviced before other low priority
264open requests (potentially spamming the cache):
265
266 aioreq_pri -3;
267 aio_open ..., sub {
268 return unless $_[0];
269
270 aioreq_pri -2;
271 aio_read $_[0], ..., sub {
272 ...
273 };
274 };
275
276
277=item aioreq_nice $pri_adjust
278
279Similar to C<aioreq_pri>, but subtracts the given value from the current
280priority, so the effect is cumulative.
281
122 282
123=item aio_open $pathname, $flags, $mode, $callback->($fh) 283=item aio_open $pathname, $flags, $mode, $callback->($fh)
124 284
125Asynchronously open or create a file and call the callback with a newly 285Asynchronously open or create a file and call the callback with a newly
126created filehandle for the file. 286created filehandle for the file.
132list. They are the same as used by C<sysopen>. 292list. They are the same as used by C<sysopen>.
133 293
134Likewise, C<$mode> specifies the mode of the newly created file, if it 294Likewise, C<$mode> specifies the mode of the newly created file, if it
135didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>, 295didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
136except that it is mandatory (i.e. use C<0> if you don't create new files, 296except that it is mandatory (i.e. use C<0> if you don't create new files,
137and C<0666> or C<0777> if you do). 297and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
298by the umask in effect then the request is being executed, so better never
299change the umask.
138 300
139Example: 301Example:
140 302
141 aio_open "/etc/passwd", O_RDONLY, 0, sub { 303 aio_open "/etc/passwd", O_RDONLY, 0, sub {
142 if ($_[0]) { 304 if ($_[0]) {
145 } else { 307 } else {
146 die "open failed: $!\n"; 308 die "open failed: $!\n";
147 } 309 }
148 }; 310 };
149 311
312
150=item aio_close $fh, $callback->($status) 313=item aio_close $fh, $callback->($status)
151 314
152Asynchronously close a file and call the callback with the result 315Asynchronously close a file and call the callback with the result
153code. I<WARNING:> although accepted, you should not pass in a perl 316code. I<WARNING:> although accepted, you should not pass in a perl
154filehandle here, as perl will likely close the file descriptor another 317filehandle here, as perl will likely close the file descriptor another
156C<close> or just let filehandles go out of scope. 319C<close> or just let filehandles go out of scope.
157 320
158This is supposed to be a bug in the API, so that might change. It's 321This is supposed to be a bug in the API, so that might change. It's
159therefore best to avoid this function. 322therefore best to avoid this function.
160 323
324
161=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 325=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
162 326
163=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 327=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
164 328
165Reads or writes C<length> bytes from the specified C<fh> and C<offset> 329Reads or writes C<$length> bytes from the specified C<$fh> and C<$offset>
166into the scalar given by C<data> and offset C<dataoffset> and calls the 330into the scalar given by C<$data> and offset C<$dataoffset> and calls the
167callback without the actual number of bytes read (or -1 on error, just 331callback without the actual number of bytes read (or -1 on error, just
168like the syscall). 332like the syscall).
169 333
334If C<$offset> is undefined, then the current file offset will be used (and
335updated), otherwise the file offset will not be changed by these calls.
336
337If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.
338
339If C<$dataoffset> is less than zero, it will be counted from the end of
340C<$data>.
341
170The C<$data> scalar I<MUST NOT> be modified in any way while the request 342The C<$data> scalar I<MUST NOT> be modified in any way while the request
171is outstanding. Modifying it can result in segfaults or WW3 (if the 343is outstanding. Modifying it can result in segfaults or World War III (if
172necessary/optional hardware is installed). 344the necessary/optional hardware is installed).
173 345
174Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at 346Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
175offset C<0> within the scalar: 347offset C<0> within the scalar:
176 348
177 aio_read $fh, 7, 15, $buffer, 0, sub { 349 aio_read $fh, 7, 15, $buffer, 0, sub {
178 $_[0] > 0 or die "read error: $!"; 350 $_[0] > 0 or die "read error: $!";
179 print "read $_[0] bytes: <$buffer>\n"; 351 print "read $_[0] bytes: <$buffer>\n";
180 }; 352 };
181 353
182=item aio_move $srcpath, $dstpath, $callback->($status)
183
184Try to move the I<file> (directories not supported as either source or
185destination) from C<$srcpath> to C<$dstpath> and call the callback with
186the C<0> (error) or C<-1> ok.
187
188This is a composite request that tries to rename(2) the file first. If
189rename files with C<EXDEV>, it creates the destination file with mode 0200
190and copies the contents of the source file into it using C<aio_sendfile>,
191followed by restoring atime, mtime, access mode and uid/gid, in that
192order, and unlinking the C<$srcpath>.
193
194If an error occurs, the partial destination file will be unlinked, if
195possible, except when setting atime, mtime, access mode and uid/gid, where
196errors are being ignored.
197
198=cut
199
200sub aio_move($$$) {
201 my ($src, $dst, $cb) = @_;
202
203 my $grp = aio_group;
204
205 add $grp aio_rename $src, $dst, sub {
206 if ($_[0] && $! == EXDEV) {
207 add $grp aio_open $src, O_RDONLY, 0, sub {
208 if (my $src_fh = $_[0]) {
209 my @stat = stat $src_fh;
210
211 add $grp aio_open $dst, O_WRONLY, 0200, sub {
212 if (my $dst_fh = $_[0]) {
213 add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
214 close $src_fh;
215
216 if ($_[0] == $stat[7]) {
217 utime $stat[8], $stat[9], $dst;
218 chmod $stat[2] & 07777, $dst_fh;
219 chown $stat[4], $stat[5], $dst_fh;
220 close $dst_fh;
221
222 add $grp aio_unlink $src, sub {
223 $cb->($_[0]);
224 };
225 } else {
226 my $errno = $!;
227 add $grp aio_unlink $dst, sub {
228 $! = $errno;
229 $cb->(-1);
230 };
231 }
232 };
233 } else {
234 $cb->(-1);
235 }
236 },
237
238 } else {
239 $cb->(-1);
240 }
241 };
242 } else {
243 $cb->($_[0]);
244 }
245 };
246
247 $grp
248}
249 354
250=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 355=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
251 356
252Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts 357Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
253reading at byte offset C<$in_offset>, and starts writing at the current 358reading at byte offset C<$in_offset>, and starts writing at the current
267C<$in_fh> than are written, and there is no way to find out how many 372C<$in_fh> than are written, and there is no way to find out how many
268bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only 373bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
269provides the number of bytes written to C<$out_fh>. Only if the result 374provides the number of bytes written to C<$out_fh>. Only if the result
270value equals C<$length> one can assume that C<$length> bytes have been 375value equals C<$length> one can assume that C<$length> bytes have been
271read. 376read.
377
272 378
273=item aio_readahead $fh,$offset,$length, $callback->($retval) 379=item aio_readahead $fh,$offset,$length, $callback->($retval)
274 380
275C<aio_readahead> populates the page cache with data from a file so that 381C<aio_readahead> populates the page cache with data from a file so that
276subsequent reads from that file will not block on disk I/O. The C<$offset> 382subsequent reads from that file will not block on disk I/O. The C<$offset>
282file. The current file offset of the file is left unchanged. 388file. The current file offset of the file is left unchanged.
283 389
284If that syscall doesn't exist (likely if your OS isn't Linux) it will be 390If that syscall doesn't exist (likely if your OS isn't Linux) it will be
285emulated by simply reading the data, which would have a similar effect. 391emulated by simply reading the data, which would have a similar effect.
286 392
393
287=item aio_stat $fh_or_path, $callback->($status) 394=item aio_stat $fh_or_path, $callback->($status)
288 395
289=item aio_lstat $fh, $callback->($status) 396=item aio_lstat $fh, $callback->($status)
290 397
291Works like perl's C<stat> or C<lstat> in void context. The callback will 398Works like perl's C<stat> or C<lstat> in void context. The callback will
304 aio_stat "/etc/passwd", sub { 411 aio_stat "/etc/passwd", sub {
305 $_[0] and die "stat failed: $!"; 412 $_[0] and die "stat failed: $!";
306 print "size is ", -s _, "\n"; 413 print "size is ", -s _, "\n";
307 }; 414 };
308 415
416
417=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
418
419Works like perl's C<utime> function (including the special case of $atime
420and $mtime being undef). Fractional times are supported if the underlying
421syscalls support them.
422
423When called with a pathname, uses utimes(2) if available, otherwise
424utime(2). If called on a file descriptor, uses futimes(2) if available,
425otherwise returns ENOSYS, so this is not portable.
426
427Examples:
428
429 # set atime and mtime to current time (basically touch(1)):
430 aio_utime "path", undef, undef;
431 # set atime to current time and mtime to beginning of the epoch:
432 aio_utime "path", time, undef; # undef==0
433
434
435=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
436
437Works like perl's C<chown> function, except that C<undef> for either $uid
438or $gid is being interpreted as "do not change" (but -1 can also be used).
439
440Examples:
441
442 # same as "chown root path" in the shell:
443 aio_chown "path", 0, -1;
444 # same as above:
445 aio_chown "path", 0, undef;
446
447
448=item aio_truncate $fh_or_path, $offset, $callback->($status)
449
450Works like truncate(2) or ftruncate(2).
451
452
453=item aio_chmod $fh_or_path, $mode, $callback->($status)
454
455Works like perl's C<chmod> function.
456
457
309=item aio_unlink $pathname, $callback->($status) 458=item aio_unlink $pathname, $callback->($status)
310 459
311Asynchronously unlink (delete) a file and call the callback with the 460Asynchronously unlink (delete) a file and call the callback with the
312result code. 461result code.
313 462
463
464=item aio_mknod $path, $mode, $dev, $callback->($status)
465
466[EXPERIMENTAL]
467
468Asynchronously create a device node (or fifo). See mknod(2).
469
470The only (POSIX-) portable way of calling this function is:
471
472 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
473
474
314=item aio_link $srcpath, $dstpath, $callback->($status) 475=item aio_link $srcpath, $dstpath, $callback->($status)
315 476
316Asynchronously create a new link to the existing object at C<$srcpath> at 477Asynchronously create a new link to the existing object at C<$srcpath> at
317the path C<$dstpath> and call the callback with the result code. 478the path C<$dstpath> and call the callback with the result code.
318 479
480
319=item aio_symlink $srcpath, $dstpath, $callback->($status) 481=item aio_symlink $srcpath, $dstpath, $callback->($status)
320 482
321Asynchronously create a new symbolic link to the existing object at C<$srcpath> at 483Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
322the path C<$dstpath> and call the callback with the result code. 484the path C<$dstpath> and call the callback with the result code.
323 485
486
487=item aio_readlink $path, $callback->($link)
488
489Asynchronously read the symlink specified by C<$path> and pass it to
490the callback. If an error occurs, nothing or undef gets passed to the
491callback.
492
493
324=item aio_rename $srcpath, $dstpath, $callback->($status) 494=item aio_rename $srcpath, $dstpath, $callback->($status)
325 495
326Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as 496Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
327rename(2) and call the callback with the result code. 497rename(2) and call the callback with the result code.
328 498
499
500=item aio_mkdir $pathname, $mode, $callback->($status)
501
502Asynchronously mkdir (create) a directory and call the callback with
503the result code. C<$mode> will be modified by the umask at the time the
504request is executed, so do not change your umask.
505
506
329=item aio_rmdir $pathname, $callback->($status) 507=item aio_rmdir $pathname, $callback->($status)
330 508
331Asynchronously rmdir (delete) a directory and call the callback with the 509Asynchronously rmdir (delete) a directory and call the callback with the
332result code. 510result code.
511
333 512
334=item aio_readdir $pathname, $callback->($entries) 513=item aio_readdir $pathname, $callback->($entries)
335 514
336Unlike the POSIX call of the same name, C<aio_readdir> reads an entire 515Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
337directory (i.e. opendir + readdir + closedir). The entries will not be 516directory (i.e. opendir + readdir + closedir). The entries will not be
338sorted, and will B<NOT> include the C<.> and C<..> entries. 517sorted, and will B<NOT> include the C<.> and C<..> entries.
339 518
340The callback a single argument which is either C<undef> or an array-ref 519The callback a single argument which is either C<undef> or an array-ref
341with the filenames. 520with the filenames.
342 521
522
523=item aio_load $path, $data, $callback->($status)
524
525This is a composite request that tries to fully load the given file into
526memory. Status is the same as with aio_read.
527
528=cut
529
530sub aio_load($$;$) {
531 aio_block {
532 my ($path, undef, $cb) = @_;
533 my $data = \$_[1];
534
535 my $pri = aioreq_pri;
536 my $grp = aio_group $cb;
537
538 aioreq_pri $pri;
539 add $grp aio_open $path, O_RDONLY, 0, sub {
540 my $fh = shift
541 or return $grp->result (-1);
542
543 aioreq_pri $pri;
544 add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
545 $grp->result ($_[0]);
546 };
547 };
548
549 $grp
550 }
551}
552
553=item aio_copy $srcpath, $dstpath, $callback->($status)
554
555Try to copy the I<file> (directories not supported as either source or
556destination) from C<$srcpath> to C<$dstpath> and call the callback with
557the C<0> (error) or C<-1> ok.
558
559This is a composite request that it creates the destination file with
560mode 0200 and copies the contents of the source file into it using
561C<aio_sendfile>, followed by restoring atime, mtime, access mode and
562uid/gid, in that order.
563
564If an error occurs, the partial destination file will be unlinked, if
565possible, except when setting atime, mtime, access mode and uid/gid, where
566errors are being ignored.
567
568=cut
569
570sub aio_copy($$;$) {
571 aio_block {
572 my ($src, $dst, $cb) = @_;
573
574 my $pri = aioreq_pri;
575 my $grp = aio_group $cb;
576
577 aioreq_pri $pri;
578 add $grp aio_open $src, O_RDONLY, 0, sub {
579 if (my $src_fh = $_[0]) {
580 my @stat = stat $src_fh;
581
582 aioreq_pri $pri;
583 add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
584 if (my $dst_fh = $_[0]) {
585 aioreq_pri $pri;
586 add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
587 if ($_[0] == $stat[7]) {
588 $grp->result (0);
589 close $src_fh;
590
591 # those should not normally block. should. should.
592 utime $stat[8], $stat[9], $dst;
593 chmod $stat[2] & 07777, $dst_fh;
594 chown $stat[4], $stat[5], $dst_fh;
595 close $dst_fh;
596 } else {
597 $grp->result (-1);
598 close $src_fh;
599 close $dst_fh;
600
601 aioreq $pri;
602 add $grp aio_unlink $dst;
603 }
604 };
605 } else {
606 $grp->result (-1);
607 }
608 },
609
610 } else {
611 $grp->result (-1);
612 }
613 };
614
615 $grp
616 }
617}
618
619=item aio_move $srcpath, $dstpath, $callback->($status)
620
621Try to move the I<file> (directories not supported as either source or
622destination) from C<$srcpath> to C<$dstpath> and call the callback with
623the C<0> (error) or C<-1> ok.
624
625This is a composite request that tries to rename(2) the file first. If
626rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
627that is successful, unlinking the C<$srcpath>.
628
629=cut
630
631sub aio_move($$;$) {
632 aio_block {
633 my ($src, $dst, $cb) = @_;
634
635 my $pri = aioreq_pri;
636 my $grp = aio_group $cb;
637
638 aioreq_pri $pri;
639 add $grp aio_rename $src, $dst, sub {
640 if ($_[0] && $! == EXDEV) {
641 aioreq_pri $pri;
642 add $grp aio_copy $src, $dst, sub {
643 $grp->result ($_[0]);
644
645 if (!$_[0]) {
646 aioreq_pri $pri;
647 add $grp aio_unlink $src;
648 }
649 };
650 } else {
651 $grp->result ($_[0]);
652 }
653 };
654
655 $grp
656 }
657}
658
343=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 659=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
344 660
345Scans a directory (similar to C<aio_readdir>) but additionally tries to 661Scans a directory (similar to C<aio_readdir>) but additionally tries to
346separate the entries of directory C<$path> into two sets of names, ones 662efficiently separate the entries of directory C<$path> into two sets of
347you can recurse into (directories or links to them), and ones you cannot 663names, directories you can recurse into (directories), and ones you cannot
348recurse into (everything else). 664recurse into (everything else, including symlinks to directories).
349 665
350C<aio_scandir> is a composite request that consists of many sub 666C<aio_scandir> is a composite request that creates of many sub requests_
351requests. C<$maxreq> specifies the maximum number of outstanding aio 667C<$maxreq> specifies the maximum number of outstanding aio requests that
352requests that this function generates. If it is C<< <= 0 >>, then a 668this function generates. If it is C<< <= 0 >>, then a suitable default
353suitable default will be chosen (currently 8). 669will be chosen (currently 4).
354 670
355On error, the callback is called without arguments, otherwise it receives 671On error, the callback is called without arguments, otherwise it receives
356two array-refs with path-relative entry names. 672two array-refs with path-relative entry names.
357 673
358Example: 674Example:
392as those tend to return 0 or 1 as link counts, which disables the 708as those tend to return 0 or 1 as link counts, which disables the
393directory counting heuristic. 709directory counting heuristic.
394 710
395=cut 711=cut
396 712
397sub aio_scandir($$$) { 713sub aio_scandir($$;$) {
714 aio_block {
398 my ($path, $maxreq, $cb) = @_; 715 my ($path, $maxreq, $cb) = @_;
399 716
717 my $pri = aioreq_pri;
718
400 my $grp = aio_group; 719 my $grp = aio_group $cb;
401 720
402 $maxreq = 8 if $maxreq <= 0; 721 $maxreq = 4 if $maxreq <= 0;
403 722
404 # stat once 723 # stat once
724 aioreq_pri $pri;
405 add $grp aio_stat $path, sub { 725 add $grp aio_stat $path, sub {
406 return $cb->() if $_[0]; 726 return $grp->result () if $_[0];
407 my $now = time; 727 my $now = time;
408 my $hash1 = join ":", (stat _)[0,1,3,7,9]; 728 my $hash1 = join ":", (stat _)[0,1,3,7,9];
409 729
410 # read the directory entries 730 # read the directory entries
731 aioreq_pri $pri;
411 add $grp aio_readdir $path, sub { 732 add $grp aio_readdir $path, sub {
412 my $entries = shift 733 my $entries = shift
413 or return $cb->(); 734 or return $grp->result ();
414 735
415 # stat the dir another time 736 # stat the dir another time
737 aioreq_pri $pri;
416 add $grp aio_stat $path, sub { 738 add $grp aio_stat $path, sub {
417 my $hash2 = join ":", (stat _)[0,1,3,7,9]; 739 my $hash2 = join ":", (stat _)[0,1,3,7,9];
418 740
419 my $ndirs; 741 my $ndirs;
420 742
421 # take the slow route if anything looks fishy 743 # take the slow route if anything looks fishy
422 if ($hash1 ne $hash2 or (stat _)[9] == $now) { 744 if ($hash1 ne $hash2 or (stat _)[9] == $now) {
423 $ndirs = -1; 745 $ndirs = -1;
424 } else { 746 } else {
425 # if nlink == 2, we are finished 747 # if nlink == 2, we are finished
426 # on non-posix-fs's, we rely on nlink < 2 748 # on non-posix-fs's, we rely on nlink < 2
427 $ndirs = (stat _)[3] - 2 749 $ndirs = (stat _)[3] - 2
428 or return $cb->([], $entries); 750 or return $grp->result ([], $entries);
429 }
430
431 # sort into likely dirs and likely nondirs
432 # dirs == files without ".", short entries first
433 $entries = [map $_->[0],
434 sort { $b->[1] cmp $a->[1] }
435 map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
436 @$entries];
437
438 my (@dirs, @nondirs);
439
440 my ($statcb, $schedcb);
441 my $nreq = 0;
442
443 $schedcb = sub {
444 if (@$entries) {
445 if ($nreq < $maxreq) {
446 my $ent = pop @$entries;
447 $nreq++;
448 add $grp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
449 }
450 } elsif (!$nreq) {
451 # finished
452 undef $statcb;
453 undef $schedcb;
454 $cb->(\@dirs, \@nondirs) if $cb;
455 undef $cb;
456 } 751 }
752
753 # sort into likely dirs and likely nondirs
754 # dirs == files without ".", short entries first
755 $entries = [map $_->[0],
756 sort { $b->[1] cmp $a->[1] }
757 map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
758 @$entries];
759
760 my (@dirs, @nondirs);
761
762 my $statgrp = add $grp aio_group sub {
763 $grp->result (\@dirs, \@nondirs);
764 };
765
766 limit $statgrp $maxreq;
767 feed $statgrp sub {
768 return unless @$entries;
769 my $entry = pop @$entries;
770
771 aioreq_pri $pri;
772 add $statgrp aio_stat "$path/$entry/.", sub {
773 if ($_[0] < 0) {
774 push @nondirs, $entry;
775 } else {
776 # need to check for real directory
777 aioreq_pri $pri;
778 add $statgrp aio_lstat "$path/$entry", sub {
779 if (-d _) {
780 push @dirs, $entry;
781
782 unless (--$ndirs) {
783 push @nondirs, @$entries;
784 feed $statgrp;
785 }
786 } else {
787 push @nondirs, $entry;
788 }
789 }
790 }
791 };
792 };
457 }; 793 };
458 $statcb = sub {
459 my ($status, $entry) = @_;
460
461 if ($status < 0) {
462 $nreq--;
463 push @nondirs, $entry;
464 &$schedcb;
465 } else {
466 # need to check for real directory
467 add $grp aio_lstat "$path/$entry", sub {
468 $nreq--;
469
470 if (-d _) {
471 push @dirs, $entry;
472
473 if (!--$ndirs) {
474 push @nondirs, @$entries;
475 $entries = [];
476 }
477 } else {
478 push @nondirs, $entry;
479 }
480
481 &$schedcb;
482 }
483 }
484 };
485
486 &$schedcb while @$entries && $nreq < $maxreq;
487 }; 794 };
488 }; 795 };
796
797 $grp
489 }; 798 }
799}
490 800
801=item aio_rmtree $path, $callback->($status)
802
803Delete a directory tree starting (and including) C<$path>, return the
804status of the final C<rmdir> only. This is a composite request that
805uses C<aio_scandir> to recurse into and rmdir directories, and unlink
806everything else.
807
808=cut
809
810sub aio_rmtree;
811sub aio_rmtree($;$) {
812 aio_block {
813 my ($path, $cb) = @_;
814
815 my $pri = aioreq_pri;
816 my $grp = aio_group $cb;
817
818 aioreq_pri $pri;
819 add $grp aio_scandir $path, 0, sub {
820 my ($dirs, $nondirs) = @_;
821
822 my $dirgrp = aio_group sub {
823 add $grp aio_rmdir $path, sub {
824 $grp->result ($_[0]);
825 };
826 };
827
828 (aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
829 (aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
830
831 add $grp $dirgrp;
832 };
833
491 $grp 834 $grp
835 }
492} 836}
493 837
494=item aio_fsync $fh, $callback->($status) 838=item aio_fsync $fh, $callback->($status)
495 839
496Asynchronously call fsync on the given filehandle and call the callback 840Asynchronously call fsync on the given filehandle and call the callback
502callback with the fdatasync result code. 846callback with the fdatasync result code.
503 847
504If this call isn't available because your OS lacks it or it couldn't be 848If this call isn't available because your OS lacks it or it couldn't be
505detected, it will be emulated by calling C<fsync> instead. 849detected, it will be emulated by calling C<fsync> instead.
506 850
507=item aio_group $callback->() 851=item aio_group $callback->(...)
508
509[EXPERIMENTAL]
510 852
511This is a very special aio request: Instead of doing something, it is a 853This is a very special aio request: Instead of doing something, it is a
512container for other aio requests, which is useful if you want to bundle 854container for other aio requests, which is useful if you want to bundle
513many requests into a single, composite, request. 855many requests into a single, composite, request with a definite callback
856and the ability to cancel the whole request with its subrequests.
514 857
515Returns an object of class L<IO::AIO::GRP>. See its documentation below 858Returns an object of class L<IO::AIO::GRP>. See its documentation below
516for more info. 859for more info.
517 860
518Example: 861Example:
524 add $grp 867 add $grp
525 (aio_stat ...), 868 (aio_stat ...),
526 (aio_stat ...), 869 (aio_stat ...),
527 ...; 870 ...;
528 871
872=item aio_nop $callback->()
873
874This is a special request - it does nothing in itself and is only used for
875side effects, such as when you want to add a dummy request to a group so
876that finishing the requests in the group depends on executing the given
877code.
878
879While this request does nothing, it still goes through the execution
880phase and still requires a worker thread. Thus, the callback will not
881be executed immediately but only after other requests in the queue have
882entered their execution phase. This can be used to measure request
883latency.
884
529=item aio_sleep $fractional_seconds, $callback->() *NOT EXPORTED* 885=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
530 886
531Mainly used for debugging and benchmarking, this aio request puts one of 887Mainly used for debugging and benchmarking, this aio request puts one of
532the request workers to sleep for the given time. 888the request workers to sleep for the given time.
533 889
890While it is theoretically handy to have simple I/O scheduling requests
891like sleep and file handle readable/writable, the overhead this creates is
892immense (it blocks a thread for a long time) so do not use this function
893except to put your application under artificial I/O pressure.
894
534=back 895=back
535 896
536=head2 IO::AIO::REQ CLASS 897=head2 IO::AIO::REQ CLASS
537 898
538All non-aggregate C<aio_*> functions return an object of this class when 899All non-aggregate C<aio_*> functions return an object of this class when
539called in non-void context. 900called in non-void context.
540 901
541A request always moves through the following five states in its lifetime,
542in order: B<ready> (request has been created, but has not been executed
543yet), B<execute> (request is currently being executed), B<pending>
544(request has been executed but callback has not been called yet),
545B<result> (results are being processed synchronously, includes calling the
546callback) and B<done> (request has reached the end of its lifetime and
547holds no resources anymore).
548
549=over 4 902=over 4
550 903
551=item $req->cancel 904=item cancel $req
552 905
553Cancels the request, if possible. Has the effect of skipping execution 906Cancels the request, if possible. Has the effect of skipping execution
554when entering the B<execute> state and skipping calling the callback when 907when entering the B<execute> state and skipping calling the callback when
555entering the the B<result> state, but will leave the request otherwise 908entering the the B<result> state, but will leave the request otherwise
556untouched. That means that requests that currently execute will not be 909untouched. That means that requests that currently execute will not be
557stopped and resources held by the request will not be freed prematurely. 910stopped and resources held by the request will not be freed prematurely.
558 911
912=item cb $req $callback->(...)
913
914Replace (or simply set) the callback registered to the request.
915
559=back 916=back
560 917
561=head2 IO::AIO::GRP CLASS 918=head2 IO::AIO::GRP CLASS
562 919
563This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to 920This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
577You add requests by calling the C<add> method with one or more 934You add requests by calling the C<add> method with one or more
578C<IO::AIO::REQ> objects: 935C<IO::AIO::REQ> objects:
579 936
580 $grp->add (aio_unlink "..."); 937 $grp->add (aio_unlink "...");
581 938
582 add $grp aio_stat "...", sub { ... }; 939 add $grp aio_stat "...", sub {
940 $_[0] or return $grp->result ("error");
941
942 # add another request dynamically, if first succeeded
943 add $grp aio_open "...", sub {
944 $grp->result ("ok");
945 };
946 };
583 947
584This makes it very easy to create composite requests (see the source of 948This makes it very easy to create composite requests (see the source of
585C<aio_move> for an application) that work and feel like simple requests. 949C<aio_move> for an application) that work and feel like simple requests.
586 950
951=over 4
952
587The IO::AIO::GRP objects will be cleaned up during calls to 953=item * The IO::AIO::GRP objects will be cleaned up during calls to
588C<IO::AIO::poll_cb>, just like any other request. 954C<IO::AIO::poll_cb>, just like any other request.
589 955
590They can be canceled like any other request. Canceling will cancel not 956=item * They can be canceled like any other request. Canceling will cancel not
591just the request itself, but also all requests it contains. 957only the request itself, but also all requests it contains.
592 958
593They can also can also be added to other IO::AIO::GRP objects. 959=item * They can also can also be added to other IO::AIO::GRP objects.
960
961=item * You must not add requests to a group from within the group callback (or
962any later time).
963
964=back
594 965
595Their lifetime, simplified, looks like this: when they are empty, they 966Their lifetime, simplified, looks like this: when they are empty, they
596will finish very quickly. If they contain only requests that are in the 967will finish very quickly. If they contain only requests that are in the
597C<done> state, they will also finish. Otherwise they will continue to 968C<done> state, they will also finish. Otherwise they will continue to
598exist. 969exist.
599 970
971That means after creating a group you have some time to add requests. And
972in the callbacks of those requests, you can add further requests to the
973group. And only when all those requests have finished will the the group
974itself finish.
975
600=over 4 976=over 4
601 977
978=item add $grp ...
979
602=item $grp->add (...) 980=item $grp->add (...)
603 981
604=item add $grp ... 982Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
983be added, including other groups, as long as you do not create circular
984dependencies.
605 985
606Add one or more 986Returns all its arguments.
607Cancels the request, if possible. Has the effect of skipping execution 987
608when entering the B<execute> state and skipping calling the callback when 988=item $grp->cancel_subs
609entering the the B<result> state, but will leave the request otherwise 989
610untouched. That means that requests that currently execute will not be 990Cancel all subrequests and clears any feeder, but not the group request
611stopped and resources held by the request will not be freed prematurely. 991itself. Useful when you queued a lot of events but got a result early.
992
993=item $grp->result (...)
994
995Set the result value(s) that will be passed to the group callback when all
996subrequests have finished and set thre groups errno to the current value
997of errno (just like calling C<errno> without an error number). By default,
998no argument will be passed and errno is zero.
999
1000=item $grp->errno ([$errno])
1001
1002Sets the group errno value to C<$errno>, or the current value of errno
1003when the argument is missing.
1004
1005Every aio request has an associated errno value that is restored when
1006the callback is invoked. This method lets you change this value from its
1007default (0).
1008
1009Calling C<result> will also set errno, so make sure you either set C<$!>
1010before the call to C<result>, or call c<errno> after it.
1011
1012=item feed $grp $callback->($grp)
1013
1014Sets a feeder/generator on this group: every group can have an attached
1015generator that generates requests if idle. The idea behind this is that,
1016although you could just queue as many requests as you want in a group,
1017this might starve other requests for a potentially long time. For
1018example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
1019requests, delaying any later requests for a long time.
1020
1021To avoid this, and allow incremental generation of requests, you can
1022instead a group and set a feeder on it that generates those requests. The
1023feed callback will be called whenever there are few enough (see C<limit>,
1024below) requests active in the group itself and is expected to queue more
1025requests.
1026
1027The feed callback can queue as many requests as it likes (i.e. C<add> does
1028not impose any limits).
1029
1030If the feed does not queue more requests when called, it will be
1031automatically removed from the group.
1032
1033If the feed limit is C<0>, it will be set to C<2> automatically.
1034
1035Example:
1036
1037 # stat all files in @files, but only ever use four aio requests concurrently:
1038
1039 my $grp = aio_group sub { print "finished\n" };
1040 limit $grp 4;
1041 feed $grp sub {
1042 my $file = pop @files
1043 or return;
1044
1045 add $grp aio_stat $file, sub { ... };
1046 };
1047
1048=item limit $grp $num
1049
1050Sets the feeder limit for the group: The feeder will be called whenever
1051the group contains less than this many requests.
1052
1053Setting the limit to C<0> will pause the feeding process.
612 1054
613=back 1055=back
614 1056
615=head2 SUPPORT FUNCTIONS 1057=head2 SUPPORT FUNCTIONS
1058
1059=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
616 1060
617=over 4 1061=over 4
618 1062
619=item $fileno = IO::AIO::poll_fileno 1063=item $fileno = IO::AIO::poll_fileno
620 1064
625 1069
626See C<poll_cb> for an example. 1070See C<poll_cb> for an example.
627 1071
628=item IO::AIO::poll_cb 1072=item IO::AIO::poll_cb
629 1073
630Process all outstanding events on the result pipe. You have to call this 1074Process some outstanding events on the result pipe. You have to call this
631regularly. Returns the number of events processed. Returns immediately 1075regularly. Returns the number of events processed. Returns immediately
632when no events are outstanding. 1076when no events are outstanding. The amount of events processed depends on
1077the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1078
1079If not all requests were processed for whatever reason, the filehandle
1080will still be ready when C<poll_cb> returns.
633 1081
634Example: Install an Event watcher that automatically calls 1082Example: Install an Event watcher that automatically calls
635IO::AIO::poll_cb with high priority: 1083IO::AIO::poll_cb with high priority:
636 1084
637 Event->io (fd => IO::AIO::poll_fileno, 1085 Event->io (fd => IO::AIO::poll_fileno,
638 poll => 'r', async => 1, 1086 poll => 'r', async => 1,
639 cb => \&IO::AIO::poll_cb); 1087 cb => \&IO::AIO::poll_cb);
640 1088
1089=item IO::AIO::max_poll_reqs $nreqs
1090
1091=item IO::AIO::max_poll_time $seconds
1092
1093These set the maximum number of requests (default C<0>, meaning infinity)
1094that are being processed by C<IO::AIO::poll_cb> in one call, respectively
1095the maximum amount of time (default C<0>, meaning infinity) spent in
1096C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
1097of time C<poll_cb> is allowed to use).
1098
1099Setting C<max_poll_time> to a non-zero value creates an overhead of one
1100syscall per request processed, which is not normally a problem unless your
1101callbacks are really really fast or your OS is really really slow (I am
1102not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
1103
1104Setting these is useful if you want to ensure some level of
1105interactiveness when perl is not fast enough to process all requests in
1106time.
1107
1108For interactive programs, values such as C<0.01> to C<0.1> should be fine.
1109
1110Example: Install an Event watcher that automatically calls
1111IO::AIO::poll_cb with low priority, to ensure that other parts of the
1112program get the CPU sometimes even under high AIO load.
1113
1114 # try not to spend much more than 0.1s in poll_cb
1115 IO::AIO::max_poll_time 0.1;
1116
1117 # use a low priority so other tasks have priority
1118 Event->io (fd => IO::AIO::poll_fileno,
1119 poll => 'r', nice => 1,
1120 cb => &IO::AIO::poll_cb);
1121
641=item IO::AIO::poll_wait 1122=item IO::AIO::poll_wait
642 1123
1124If there are any outstanding requests and none of them in the result
643Wait till the result filehandle becomes ready for reading (simply does a 1125phase, wait till the result filehandle becomes ready for reading (simply
644C<select> on the filehandle. This is useful if you want to synchronously wait 1126does a C<select> on the filehandle. This is useful if you want to
645for some requests to finish). 1127synchronously wait for some requests to finish).
646 1128
647See C<nreqs> for an example. 1129See C<nreqs> for an example.
648 1130
1131=item IO::AIO::poll
1132
1133Waits until some requests have been handled.
1134
1135Returns the number of requests processed, but is otherwise strictly
1136equivalent to:
1137
1138 IO::AIO::poll_wait, IO::AIO::poll_cb
1139
649=item IO::AIO::nreqs 1140=item IO::AIO::flush
650 1141
651Returns the number of requests currently outstanding (i.e. for which their 1142Wait till all outstanding AIO requests have been handled.
652callback has not been invoked yet).
653 1143
654Example: wait till there are no outstanding requests anymore: 1144Strictly equivalent to:
655 1145
656 IO::AIO::poll_wait, IO::AIO::poll_cb 1146 IO::AIO::poll_wait, IO::AIO::poll_cb
657 while IO::AIO::nreqs; 1147 while IO::AIO::nreqs;
658 1148
659=item IO::AIO::flush 1149=back
660 1150
661Wait till all outstanding AIO requests have been handled. 1151=head3 CONTROLLING THE NUMBER OF THREADS
662 1152
663Strictly equivalent to: 1153=over
664
665 IO::AIO::poll_wait, IO::AIO::poll_cb
666 while IO::AIO::nreqs;
667
668=item IO::AIO::poll
669
670Waits until some requests have been handled.
671
672Strictly equivalent to:
673
674 IO::AIO::poll_wait, IO::AIO::poll_cb
675 if IO::AIO::nreqs;
676 1154
677=item IO::AIO::min_parallel $nthreads 1155=item IO::AIO::min_parallel $nthreads
678 1156
679Set the minimum number of AIO threads to C<$nthreads>. The current default 1157Set the minimum number of AIO threads to C<$nthreads>. The current
680is C<4>, which means four asynchronous operations can be done at one time 1158default is C<8>, which means eight asynchronous operations can execute
681(the number of outstanding operations, however, is unlimited). 1159concurrently at any one time (the number of outstanding requests,
1160however, is unlimited).
682 1161
683IO::AIO starts threads only on demand, when an AIO request is queued and 1162IO::AIO starts threads only on demand, when an AIO request is queued and
684no free thread exists. 1163no free thread exists. Please note that queueing up a hundred requests can
1164create demand for a hundred threads, even if it turns out that everything
1165is in the cache and could have been processed faster by a single thread.
685 1166
686It is recommended to keep the number of threads low, as some Linux 1167It is recommended to keep the number of threads relatively low, as some
687kernel versions will scale negatively with the number of threads (higher 1168Linux kernel versions will scale negatively with the number of threads
688parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32 1169(higher parallelity => MUCH higher latency). With current Linux 2.6
689threads should be fine. 1170versions, 4-32 threads should be fine.
690 1171
691Under most circumstances you don't need to call this function, as the 1172Under most circumstances you don't need to call this function, as the
692module selects a default that is suitable for low to moderate load. 1173module selects a default that is suitable for low to moderate load.
693 1174
694=item IO::AIO::max_parallel $nthreads 1175=item IO::AIO::max_parallel $nthreads
703This module automatically runs C<max_parallel 0> at program end, to ensure 1184This module automatically runs C<max_parallel 0> at program end, to ensure
704that all threads are killed and that there are no outstanding requests. 1185that all threads are killed and that there are no outstanding requests.
705 1186
706Under normal circumstances you don't need to call this function. 1187Under normal circumstances you don't need to call this function.
707 1188
1189=item IO::AIO::max_idle $nthreads
1190
1191Limit the number of threads (default: 4) that are allowed to idle (i.e.,
1192threads that did not get a request to process within 10 seconds). That
1193means if a thread becomes idle while C<$nthreads> other threads are also
1194idle, it will free its resources and exit.
1195
1196This is useful when you allow a large number of threads (e.g. 100 or 1000)
1197to allow for extremely high load situations, but want to free resources
1198under normal circumstances (1000 threads can easily consume 30MB of RAM).
1199
1200The default is probably ok in most situations, especially if thread
1201creation is fast. If thread creation is very slow on your system you might
1202want to use larger values.
1203
708=item $oldnreqs = IO::AIO::max_outstanding $nreqs 1204=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
1205
1206This is a very bad function to use in interactive programs because it
1207blocks, and a bad way to reduce concurrency because it is inexact: Better
1208use an C<aio_group> together with a feed callback.
709 1209
710Sets the maximum number of outstanding requests to C<$nreqs>. If you 1210Sets the maximum number of outstanding requests to C<$nreqs>. If you
711try to queue up more than this number of requests, the caller will block until 1211to queue up more than this number of requests, the next call to the
712some requests have been handled. 1212C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1213function will block until the limit is no longer exceeded.
713 1214
714The default is very large, so normally there is no practical limit. If you 1215The default value is very large, so there is no practical limit on the
715queue up many requests in a loop it often improves speed if you set 1216number of outstanding requests.
716this to a relatively low number, such as C<100>.
717 1217
718Under normal circumstances you don't need to call this function. 1218You can still queue as many requests as you want. Therefore,
1219C<max_oustsanding> is mainly useful in simple scripts (with low values) or
1220as a stop gap to shield against fatal memory overflow (with large values).
1221
1222=back
1223
1224=head3 STATISTICAL INFORMATION
1225
1226=over
1227
1228=item IO::AIO::nreqs
1229
1230Returns the number of requests currently in the ready, execute or pending
1231states (i.e. for which their callback has not been invoked yet).
1232
1233Example: wait till there are no outstanding requests anymore:
1234
1235 IO::AIO::poll_wait, IO::AIO::poll_cb
1236 while IO::AIO::nreqs;
1237
1238=item IO::AIO::nready
1239
1240Returns the number of requests currently in the ready state (not yet
1241executed).
1242
1243=item IO::AIO::npending
1244
1245Returns the number of requests currently in the pending state (executed,
1246but not yet processed by poll_cb).
719 1247
720=back 1248=back
721 1249
722=cut 1250=cut
723 1251
735 or return undef; 1263 or return undef;
736 1264
737 *$sym 1265 *$sym
738} 1266}
739 1267
740min_parallel 4; 1268min_parallel 8;
741 1269
742END { 1270END { flush }
743 max_parallel 0;
744}
745 1271
7461; 12721;
747 1273
748=head2 FORK BEHAVIOUR 1274=head2 FORK BEHAVIOUR
749 1275
750This module should do "the right thing" when the process using it forks: 1276This module should do "the right thing" when the process using it forks:
751 1277
752Before the fork, IO::AIO enters a quiescent state where no requests 1278Before the fork, IO::AIO enters a quiescent state where no requests
753can be added in other threads and no results will be processed. After 1279can be added in other threads and no results will be processed. After
754the fork the parent simply leaves the quiescent state and continues 1280the fork the parent simply leaves the quiescent state and continues
755request/result processing, while the child clears the request/result 1281request/result processing, while the child frees the request/result queue
756queue (so the requests started before the fork will only be handled in 1282(so that the requests started before the fork will only be handled in the
757the parent). Threads will be started on demand until the limit ste in the 1283parent). Threads will be started on demand until the limit set in the
758parent process has been reached again. 1284parent process has been reached again.
759 1285
760In short: the parent will, after a short pause, continue as if fork had 1286In short: the parent will, after a short pause, continue as if fork had
761not been called, while the child will act as if IO::AIO has not been used 1287not been called, while the child will act as if IO::AIO has not been used
762yet. 1288yet.
763 1289
1290=head2 MEMORY USAGE
1291
1292Per-request usage:
1293
1294Each aio request uses - depending on your architecture - around 100-200
1295bytes of memory. In addition, stat requests need a stat buffer (possibly
1296a few hundred bytes), readdir requires a result buffer and so on. Perl
1297scalars and other data passed into aio requests will also be locked and
1298will consume memory till the request has entered the done state.
1299
1300This is not awfully much, so queuing lots of requests is not usually a
1301problem.
1302
1303Per-thread usage:
1304
1305In the execution phase, some aio requests require more memory for
1306temporary buffers, and each thread requires a stack and other data
1307structures (usually around 16k-128k, depending on the OS).
1308
1309=head1 KNOWN BUGS
1310
1311Known bugs will be fixed in the next release.
1312
764=head1 SEE ALSO 1313=head1 SEE ALSO
765 1314
766L<Coro>, L<Linux::AIO> (obsolete). 1315L<Coro::AIO>.
767 1316
768=head1 AUTHOR 1317=head1 AUTHOR
769 1318
770 Marc Lehmann <schmorp@schmorp.de> 1319 Marc Lehmann <schmorp@schmorp.de>
771 http://home.schmorp.de/ 1320 http://home.schmorp.de/

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